K11 Owners Group

Flying Duck · Posted: Sun Dec 26, 2010 4:53 pm Post subject: Variable Heated Grips

The early K bikes (and some Rs too) OEM heated grips have a resistive wire that the current runs through when you use the low setting. This drops the voltage and reduces the heat from the grips. The downside of this is that when used for an extended period that wire can heat up, melt it's insulation, short out and let some of the magic smoke out of the electrical system before blowing the number 1 fuse. This happens to the intermediate wiring harness (part number 61121459263) that connects the switch and the heated grips to the main wiring harness.

This happened to me a couple of years ago. I replaced the intermediate wiring harness but have not used the low setting since then because I don't want to risk this happening again so I just use the full setting. Since I don't always need full heat from the grips it's a minor annoyance to have to be turning them on and off when it's only moderately cold.

The answer? Get rid of the intermediate wiring harness altogether and replace the heated grip switch with a variable PWM switch. PWM is pulse width modulation. Instead of supplying 12V all of the time the switch varies the amount of time that 12V is output. For example, a PWM set at 50% only delivers 12V half of the time, effectively reducing the voltage to 6V.

The OEM heated grips draw something like 50 or 60 watts so I found this PWM switch on Fleabay which has a capacity of 76 watts:
http://cgi.ebay.com/ebaymotors/PWM-dimmer-switch-12v-DC-LED-and-panel-lights-6-amp-_W0QQcmdZViewItemQQhashZitem1e6059cb44QQitemZ130465516356QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories#ht_583wt_911

The back of the circuit board already had some protective stuff on but the side with the components did not. With a toothpick I applied some epoxy to all of the exposed electircal connections on the front of it to make it water resistant/proof.

Then I mounted it in a carefully mutilated OEM switch blank and had to cut some stuff out of the handlebar cover from behind but was able to get it to fit where I wanted it

Here's what it looks like from behind:

I went through all of the 1/4" core knobs at McMaster-Carr to find one that I thought would work well with gloves on. It looked kind of cheesy with a silver center so I glued on a city case roundel to gussy it up a bit.

I also epoxied a 3mm green LED into the top of the switch blank and hooked that up to the output. It's gets brighter the higher you turn up the PWM switch. I did that since this in kind of a prototype and the LED gives me visual confirmation that it's still working.

Voila! Variable heated grips. Very Happy

_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

whyoldbill · Posted: Sun Dec 26, 2010 6:05 pm Post subject:

When does the Flying Duck grip heat control kit go on sale?
_________________
'02 - GL1800

The desired effect is what you get when you improve your interplanetary funksmanship - George Clinton

SugarHillCTD · Posted: Sun Dec 26, 2010 6:15 pm Post subject:

NICE mod.

If I had kept the Concours longer that was on my list- since I had added grip heaters to it.

Thanks for the inspiration.
_________________
John & Cathy

'92 K100RS4V Pearl White SOLD
'04 K1200GT
IBA Several-SS1k, BBG, 50CC NYC to S.F.

supercat1 · Posted: Sun Dec 26, 2010 11:44 pm Post subject:

so does it smooth the output within the pwm switch or is it actually pulsing to the grips? i don't know much about how well circuits deal with cyclic loading, just as a structural engineer that is one way that leads to failure of a structure. just curious.
_________________
(formerly) 1993 k1100rs

drikko · Posted: Mon Dec 27, 2010 12:26 am Post subject:

A purely resistive element like the heaters in the grips won't care about the switching off and on whether it fast or slow, the heat output is smoothed by thermal momentum in the element and grip so it's not a problem. Same as a filament light bulb. BTW in effect this is how light dimmers work except in an AC way. In this case it just chops part of the sine wave off each cycle which is why you can't use incandescent dimmer with fluorescent bulb, only filament ones.
_________________
K1100RS '97
Laverda RGS 1000 '84
Jim Young Trailer Sailer 5.7M WB

DISCLAIMER:- Anything I say may have been when I was drunk so please don't take it personally.

'Bigamy is having one wife/husband too many. Monogamy is the same.'
Oscar Wilde

Flying Duck · Posted: Mon Dec 27, 2010 12:43 am Post subject:

hfxrzw · Mad Brick Rider Joined: 30 Jan 2009 Posts: 78

A bit puzzled. I seriously like the idea, after having had to repair some of my wiring (indeed, cause as above), but the referred add says the following: "Will not work in circuits where you are grounding to the frame." Isn't that exactly how we ground our systems? How did you overcome this?
_________________
Cheers, Rene

Greetings from Florida.

BMW K100 '85

drikko · Posted: Mon Dec 27, 2010 5:48 am Post subject:

It means the load ie the grips, so make sure you put both ends of the heaters on the outlet of the PWM and don't ground either side.
_________________
K1100RS '97
Laverda RGS 1000 '84
Jim Young Trailer Sailer 5.7M WB

DISCLAIMER:- Anything I say may have been when I was drunk so please don't take it personally.

'Bigamy is having one wife/husband too many. Monogamy is the same.'
Oscar Wilde

Flying Duck · Posted: Mon Dec 27, 2010 2:05 pm Post subject:

supercat1 · Posted: Mon Dec 27, 2010 4:50 pm Post subject:

Flying Duck · Posted: Mon Dec 27, 2010 4:54 pm Post subject:

It's pulsing. Hence the name.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

supercat1 · Posted: Mon Dec 27, 2010 5:07 pm Post subject:

so your led pulses too then? interesting.
_________________
(formerly) 1993 k1100rs

Flying Duck · Posted: Mon Dec 27, 2010 5:48 pm Post subject:

Yes, the LED is pulsing. It's similar to how heated gear controllers work but at a higher frequency.

I posted this over on ADV as well. Someone suggested replacing the resistive wire in the circuit with a flasher relay. As long as you got a relay that could handle 5 amps or more I think that could also be used to get a low setting without the risk of a meltdown. Some flasher relays click, some don't. I'd go for a silent one.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Flying Duck · Posted: Sun Jan 09, 2011 10:17 pm Post subject:

I went riding with JO and MO today and got to try this mod out in varying degrees of cold weather. I'm very happy with the results because it lets me adjust the HGs to where the temperature is just right. I've got another PWM unit and am definitely going to do it to the RS as well.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

ChuckS · Posted: Mon Nov 07, 2011 11:07 pm Post subject:

Early K bike-- are we talking K75, K100, K1100....?

I guess I'm most specifically interested in my 1993 K1100LT. Winter is coming and I'm not smart enough to put the beast away. Might it melt itself on the low setting?

Thanks!!

Edit-
I found the sticky, here: http://www.k11og.org/forum/viewtopic.php?t=4199

It looks like 1993 was a bad year and might well melt itself. Variable grips, here I come!
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1993 K1100LT
04 DL650